The Delta Military Forces Drop Force is the main terrestrial invasion force of the DMF. It is the largest of the six forces, able to field 0.4 million troops more than the Defence Force. Drop Force began as the Orbital Drop unit of the Marine Corps in the Arthian Expanse AllianceSekhtokrun Retaliation Force, but over the proceeding five centuries, and during the transition from the SRF to the DMF, it has become the primary Infantry and Armour assault force.